The present invention relates to a manufacturing method for a planar photodiode with a hetero-structure formed between a layer provided with a pn junction and a layer adjacent thereto.
Photodiodes with the avalanche effect which are suitable for the wave length range up to 1.65 .mu.m and for employment in optical message transmission systems with light wave guides are known. For example, mesa diodes for this purpose are known from "Electronic Letters", Vol. 16 (1980), pages 163-165, from "IEEE Journal of Quantum Electronics", Vol. 17 (1981), pages 260-264, and "Applied Physics Letters", Vol. 39 (1981), pages 402-404, all incorporated herein by reference. Given this specific structure of the diode, indium gallium arsenide phosphide is deposited on indium phosphide in the course of a manufacturing process of the diode. Apart from the necessity of the mesa structure, the product of layer thickness and doping given this known diode is very difficult to set with the tolerance required per se.
Planar photodiodes with indium phosphide deposited on indium gallium arsenide phosphide and with a long-wave sensitivity limit above 1.36 .mu.m are manufactured with the assistance of gaseous phase epitaxy. The pn junction given these diodes is generated with the assistance of a p-doping diffusion, whereby a layer of dielectric material--such as, for example, silicon nitride--is employed as the diffusion mask. Details concerning this prior art can be derived from "IEEE Journal of Quantum Electronics", Vol. 17 (1981), page 250, incorporated herein by reference.
Constructing diodes manufactured in known manner with gaseous phase epitaxy as discussed above with the assistance of liquid phase epitaxy--while still achieving at least a comparably high quality of the diodes--results in the problem that indium phosphide can only be deposited with great difficulty on an indium gallium arsenide phosphide layer with a sufficiently high arsenic content that a sufficiently high wavelength is achieved. If possible this wavelength is greater than 1.3 .mu.m.